By using a thin13Cdiamond chip together with a12Cdiamond chip as sensors, the diamond Raman spectra provide the means to measure pressure precisely (±0.3 GPa) at any temperature (10–1200 K) and simultaneous hydrostatic (or quasihydrostatic) pressure (0–25 GPa) foranysample compatible with an externally heated diamond-anvil cell. Minimum interference between the Raman spectrum from the diamond anvils and those of the pressure sensors is obtained by measuring pressures with the Raman signal from the13Cdiamond chip up to 13 GPa, and that from the12Cchip above 10 GPa. The best crystallographic orientation of the diamond anvils is with the [100] direction along the direction of applied force, in order to further minimize the interference. At 298 K, the pressure dependence of the13Cdiamond first-order Raman line is given by&ngr;(P)=&ngr;RT+aPfor 91 at. &percent;13Cdiamond, where&ngr;RT(13C)=1287.79±0.28 cm−1anda(13C)=2.83±0.05 cm−1/GPa.Analysis of values from the literature shows that the pressure dependence of the Raman line of12Cdiamond is best described by the parameters&ngr;RT(12C)=1332.5 cm−1anda(12C)=2.90±0.05 cm−1/GPa.The temperature dependence of the diamond Raman line is best described by&ngr;(T)−&ngr;RT=b0forT⩽200 K,and&ngr;(T)−&ngr;RT=b0+b1.5Tk1.5for200 K⩽T⩽1500 K,whereTk=T−200 K.For 91 at. &percent;13Cdiamond, the parameters areb0=0.450±0.025 cm−1;b1.5=−(7.36±0.09)×10−4 cm−1 K−1.5;and for12Cdiamond, the parameters areb0=0.467±0.033 cm−1,b1.5=−(7.56±0.10)×10−4 cm−1 K−1.5.Although no quantitative theoretical models are available for calculating the Raman shift as a function of temperature, the excellent fits to the data suggest that theTk1.5dependence above has a physical basis. ©1997 American Institute of Physics.